The present invention relates to failure detection and more particularly to a circuit for detecting the failure of a system to respond in a planned manner to binary control signals.
As electronic systems have become more sophisticated and complex, the risks of tampering or failure with components or circuits have increased. In such systems, component or circuit failure can result in a generated output signal which may be misinterpreted as representing a condition which does not really exist. As a simple example, the failure of a light source for a photocell might result in a signal which would normally be interpreted as an "object absent" signal when in fact an object is present.
The consequences of undetected circuit or component failure are too varied and diverse to discuss other than in a general way. Where the circuit is part of a system for recording costs or financial transactions, indefinite amounts of money may be involved. Where the circuit is part of a control system for machinery or devices, property damage or personal injury may result from undetected circuit or component failure.
Failure detection systems are, of course, known in the art. Such systems are typically complex, expensive, and capable of application only to specific systems.